Microstructural and tribological properties of high-performance Inconel 625 alloy-WS2 self-lubricious composite coating by laser assisted cold spray

A hard and self -lubricious composite coating of tungsten disulfide (WS2) blended Inconel 625 alloy was deposited on AISI 304 stainless steel substrate by laser assisted cold spray (LACS) process through optimizing the laser power and gas pressure of the supersonic jet. Effects of the laser power which determined the deposition temperature and the gas pressure of the cold spray on powder deposition were studied. The surface temperature during laser heating was maintained below the evaporation temperature of WS2 for avoiding depletion of the WS2, but sufficiently high to soften the hard Inconel 625 powder. This facilitated deposition of the blended powder through plastic deformation at a relatively low gas -jet velocity in comparison to that typically employed in a conventional cold spray process. XRD and XPS results confirmed the presence of WS2 in the coating. The coefficient of friction was found to be 5 times lower (0.11) and the wear rate 42 times lower (8.5 x10-6 mm3/N- m) than those of the substrate. The coating exhibited a hardness more than two times that of the substrate (490 HV) due to presence of nano -sized tungsten dispersed in the matrix.